When a portfolio management system processes an investment account trade order consisting of a mix of “sell” orders and “buy” orders, some of the sell orders may be prevented or blocked from being executed for a variety of reasons. Because some of the sell orders may be necessary to generate sufficient cash to fund the buy orders, the blocking of some sell orders may result in insufficient cash for executing all of the buy orders. In this situation, at least some of the buy orders may have to be canceled or reduced in order to generate a trading proposal that can be properly executed based upon the available cash.